In a battle situation it is necessary for a gun crew to be able to assess the accuracy with which rounds fired by their gun are hitting intended targets. Conventionally, this assessment has been carried out visually with the aid of binoculars or a telescope. However, visual assessment of this type is of limited use because of the momentary nature of the event being observed and because the resulting cloud of smoke and dust which is raised by the resultant explosion can easily obscure the point of impact. It is also often the case that when an incoming round has landed close to a target such as a tank, the tank crew will rapidly fire off smoke bombs to obscure them from the attacking gun, again obscuring the view of the observer. Furthermore, the observer's line-of-sight can be interrupted by smoke and dust thrown up by his own gun and by vibration produced on firing the gun.
It is known to use an image sensor (typically a thermal imager) mounted on a gun and directed at the target to record continuously while the gun is being fired. The video sequence recorded can be viewed subsequently in an attempt to assess the accuracy of fired round. The gun operator can then attempt to correct any gun targeting errors by realigning the gun barrel. However, the transient nature of the firing and impact events, as well as the relatively small size of a fired round, makes it extremely difficult for the operator to view the trajectory of the round and the point of impact. The subjective nature of this process leaves open the possibility of significant human errors being introduced in the realignment stage.
A further disadvantage if this system is that it generates a large amount of recorded data which must generally be stored on video tape, an unreliable storage medium under battlefield conditions. Whilst solid state memory may be used, this is expensive where it is required to store a long video sequence or a large number of sequences to be stored for later historical analysis. Furthermore, in order to identify that portion of the video sequence which shows the round passing or hitting the target, perhaps only one or two frames of the video sequence, the gun crew must review a relatively large number of frames. In a battle situation, the time wasted studying the sequence can be critical.